I have wondered for quite awhile why Mao is on all the modern Chinese currency. I always thought the older Chinese currency looked much better – it has pictures of various workers and ethnic minorities working in groups. Seemed a lot more socialist to me than just having Mao.
Then I learned that it was easy for people to counterfeit Chinese currency because people did not recognise characters on the different denominations of currency. Everybody knows what Mao should look like. So the standardisation on Mao helped people recognise right away if they held legit currency or not. Or at least fake currency that actually resembled the real thing.
I have had banks in China hand me some bills that were counterfeit. They had Mao, but were missing other important features. Haven’t experienced that in other countries, at least not yet.